1. Field of the Invention
The present invention relates to the production of 1,7-octadiene by hydrodimerizing butadiene.
2. Description of the Prior Art
Linear dimerization of butadiene provides a source of C.sub.8 unsaturated hydrocarbon intermediates useful for the synthesis of diacids, diesters, diols or diamines. A particularly preferred dimer is 1,7-octadiene which has terminal double bonds and allows the production of product having only terminal functional groups.
Wright in U.S. Pat. No. 3,732,328, issued May 8, 1973, prepares mixtures of octadienes by reacting butadiene in the presence of a palladium compound, a polar solvent, a reducing agent and a tertiary phosphine.
Wright in U.S. Pat. No. 3,823,199, issued July 9, 1974, prepares mixtures of octadienes by reacting butadienes in the presence of palladium metal or a palladium compound, a non-polar solvent, a reducing agent and a tertiary phosphine.
Wright in British Pat. No. 1,341,324 issued Dec. 9, 1973 discloses processes similar to above but uses amine solvents.
Gardner et al, Tetrahedron Letters No. 2, pp. 163-164 discloses the production of mixtures of octadienes by reacting butadiene in the presence of palladium salts, an organic base, formic acid and a phosphine.
Roffia et al, Journal of Organometallic Chemistry, 55 (1973) 405-407 utilizes a triphenyl phosphine-zero valent palladium complex catalyst in benzene in the presence of formic acid to dimerize butadiene. Although Roffia et al reported a 75% butadiene conversion, only 22% of the product was 1,7-octadiene.
None of the references cited above have disclosed the concept of increasing the rate of formation of 1,7-octadiene by also using a supported palladium, platinum and/or rhodium catalyst in conjunction with solubilized palladium catalyst. Increased rates are important to commercial ventures. High selectivities and conversions at low rates can make a venture unprofitable. The instant invention provides significantly enhanced rates over those of the prior art.